Kuliah 1 Mobile Computing. Basis teori Komunikasi Data. Analisa Fourier Bandwidth-Limited Signals Maximum Data Rate dari Channel. Analisa Fourier. ∞. ∞. n=1. n=1. T. 0. T. 0. T. 0. Setiap suatu fungsi periodik g(t) dengan periode T dapat dinyatakan sebagai :
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Setiapsuatufungsiperiodik g(t) denganperiode T dapatdinyatakansebagai:
g(t) = c/2 + ∑ an sin(2∏nft) + ∑ bncos(2∏nft)
Dimana: an = 2/T ∫ g(t) sin(2∏nft) dt
bn = 2/T ∫ g(t) cos(2∏nft) dt
cn = 2/T ∫ g(t) dt
A binary signal and its root-mean-square Fourier amplitudes.
(b) – (c) Successive approximations to the original signal.
(d) – (e) Successive approximations to the original signal.
Maximum data rate (C) = 2B log2 M
Maximum data rate (C) = B log2 (1+S/N)
C : kapasitas kanal (bps)
B : bandwidth (Hz)
M : jumlah level tegangan
S/N : signal to noise ratio
dalam decibel: S/N = 10 log10 S/N
B = 4 MHz – 3 MHz = 1 Mhz
S/N = 24 dB = 10 log10 S/N S/N = 251
C = 106 log2 (1+251) ≈ 106 x 8 = 8 Mbps
C = 2B log2 M
8 x 106 = 2 x 106 x log2 M
4 = log2 M M = 16
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
(a) QPSK (Quadrature Phase Shift Keying)
(b) QAM-16 (Quadrature Amplitude Modulation -16)
(c) QAM-64 (Quadrature Amplitude Modulation - 64)
The electromagnetic spectrum and its uses for communication.
(a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth.
(b) In the HF band, they bounce off the ionosphere.
Convection currents can interfere with laser communication systems.
A bidirectional system with two lasers is pictured here.
(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.
(b) Light trapped by total internal reflection.
Attenuation of light through fiber in the infrared region.
(a) Side view of a single fiber.
(b) End view of a sheath with three fibers.
(a) The original bandwidths.
(b) The bandwidths raised in frequency.
(b) The multiplexed channel.
Wavelength division multiplexing.
The T1 carrier (1.544 Mbps).
Multiplexing T1 streams into higher carriers.
(a) Binary chip sequences for four stations
(b) Bipolar chip sequences
(c) Six examples of transmissions
(d) Recovery of station C’s signal
(a) Circuit switching.
(b) Packet switching.
(a) Circuit switching (b) Message switching (c) Packet switching
A comparison of circuit switched and packet-switched networks.
(a) Frequencies are not reused in adjacent cells.
(b) To add more users, smaller cells can be used.
GSM uses 124 frequency channels, each of which uses an eight-slot TDM system
A portion of the GSM framing structure.
Basic services an IMT-2000 network should provide